title: A tunable notch filter using microelectromechanical microring with gap-variable busline coupler.
abstract: A microelectromechanical tunable notch filter using silicon-photonic freestanding waveguides is proposed, and the basic characteristics are experimentally investigated. The proposed filter is composed of a wavelength-tunable silicon microring resonator and a busline switch. The tunable microring consists of freestanding single-mode waveguides and air-gap directional waveguide couplers. The optical path length of the microring is varied physically by a displacement of electrostatic comb-drive actuator. The busline switch consists of a gap-variable waveguide coupling mechanism, which enables coupling the tunable microring with the busline by another electrostatic comb-drive actuator. During the wavelength tuning of microring, the busline can be disconnected from the microring. Therefore, the proposed device operates as a hitless wavelength-selective switch if they are connected in series. The waveguides are 320 nm in width and 340 nm in thickness. The resonant wavelength shift of the microring is 9.96 nm at the voltage of 26 V with the actuator displacement of 1.0 μm. The coupling to busline is adjusted from the switch-off state at the gap of 600 nm to the switch-on state corresponding to the critical coupling condition at the gap of 383 nm. The whole size of the wavelength-tunable filter with hitless mechanism is about 150 μm by 80 μm. Due to the capacitive operation of the comb-drive actuators, the power consumption is negligibly small.
authors.forename: Taro
authors.initials: T
authors.lastname: Ikeda
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Hane